Reply by Wiley

I’m not a lawyer, but I have a decent amount of experience in this area through my knitting and fiber arts background. Around there, the rule of thumb is that no matter how much you are altering someone’s pattern, you can’t sell it as your own. Eg. taking a pattern for a crocheted catapillar, altering the pattern to make it slightly bigger and then selling it would be a violation of copyright. If, on the other hand, you create a pattern from scratch based on looking at something and coming up with your own (“hmm, a catapillar made out of a series of crocheted balls, I know how to do that”) that’s ok.

To sum up: if you understand the mechanics of the project well enough to sit down with a blank piece of paper and draw up a plan for your project without consulting any part of the original plan you bought, you’re probably ok.

-- "When you lose the power to laugh, you lose the power to think straight" - Inherit the Wind